At present, it is known to prepare a copolymer consisting of the reaction product of bis(3,5-dimethyl-4-hydroxyphenyl)sulfone; 2,2-bis(4-hydroxyphenyl)propane and a carbonate precursor. U.S. Pat. No. 3,737,409 describes a process for making such a copolymer, which is disclosed to lend itself to the preparation of textile fibers.
U.S. Pat. No. 4,286,057 describes a molding composition comprising blends of polyarylates derived from a dihydric phenol and mixtures of terephthalic acid and isophthalic acid, and at least one thermoplastic polymer compatible therewith. A blend of the polyarylates and an aromatic polycarbonate, where a thermoplastic compatible polymer is optionally added is also mentioned.
Polyethylene terephthalate films modified with a minor amount of preferably no more than 10% bisphenol A polycarbonate resin are disclosed in U.S. Pat. No. 3,720,732. Processing difficulties were encountered when higher amounts of the resin were included. In any event, when the working composition of U.S. Pat. No. 3,720,732 are made, a compatible composition in the sense contemplated by the present invention is not obtained when the amount of polycarbonate resin exceeds as little as 5% by weight of the combined amounts of polycarbonate and polyester.
In applicants' issued application, Ser. No. 451,181, filed Dec. 20, 1982, now U.S. Pat. No. 4,511,693, there are disclosed and claimed novel compositions comprising mixed polycarbonates and thermoplastic addition polymers containing hetero groups which are admixed to provide compatible compositions.